Spacing effect
The spacing effect refers in psychology to the observed phenomenon that items that are repeated during list learning are remembered better if their two presentations are spread out over time (spaced presentation) than immediately one after the other (massed presentation). This robust phenomenon is found in many explicit memory tasks such as free recall, recognition, cued-recall, and frequency estimation (for reviews see Crowder 1976; Greene, 1989). For studying, this effect suggests that "cramming" (intense, last-minute studying) the night before an exam is not likely to be as effective as studying at intervals over a much longer span of time. Several possible explanations of the spacing effect have been offered. According to the deficient processing view, massed repetition leads to only one representation of the material in memory, whereas spaced repetition creates a new representation for the second presentation, thus doubling representations and bolstering the memory. However, according to the encoding variability view, spaced repetition is likely to entail some variability in presentation; this then leads to a more robust memory which is more connected to other ideas. The robustness of the phenomenon and its resistance to experimental manipulation have made empirical testing of its parameters difficult. Research overview Multiple theories have been proposed to explain the spacing effect, and it is now believed that an appropriate account should be multifactorial, and at present, different mechanisms are invoked to account for the spacing effect in free recall and in explicit cued-memory tasks. Greene (1989) proposed a two-factor account of the spacing effect, combining deficient processing and study-phase retrieval accounts. Spacing effects in free recall are accounted for by the study-phase retrieval account. Under the assumption that free recall is sensitive to contextual associations, spaced items are advantaged by additional encoding of contextual information relative to massed items. Thus, the second occurrence of an item in a list reminds the observer of the previous occurrence of the same item and of the contextual features surrounding that item. When items are presented in a spaced manner, different contextual information is encoded with each presentation, whereas for massed items, the difference in context is relatively small. This leads to more retrieval cues being encoded with spaced relative to massed items, leading to improved recall. For cued-memory tasks (e.g. recognition memory, frequency estimation tasks), which rely more on item information and less on contextual information, Greene (1989) proposed that the spacing effect is due to the deficient processing of the second occurrence of a massed item. This deficient processing is due to the increased amount of voluntary rehearsal of spaced items. This account is supported by findings that the spacing effect is not found when items are studied through incidental learning. However, research has shown reliable spacing effects in cued-memory tasks under incidental learning conditions, where semantic analysis is encouraged through orienting tasks (Challis, 1993; Russo & Mammaralla, 2002). Challis found a spacing effect for target words using a frequency estimation task after words were incidentally analyzed semantically. However, no spacing effect was found when the target words were shallowly encoded using a graphemic study task. This suggests that semantic priming underlies the spacing effect in cued-memory tasks. When items are presented in a massed fashion, the first occurrence of the target semantically primes the mental representation of that target, such that when the second occurrence appears directly after the first, there is a reduction in its semantic processing. Semantic priming wears off after a period of time (Kirsner, Smith, Lockhart, & King, 1984), which is why there is less semantic priming of the second occurrence of a spaced item. Thus on the semantic priming account, the second presentation is more strongly primed and receives less semantic processing when the repetitions are massed compared to when presentations are spaced over short lags (Challis, 1993). This semantic priming mechanism provides spaced words with more extensive processing than massed words, producing the spacing effect. From this explanation of the spacing effect, it follows that this effect should not occur with nonsense stimuli that do not have a semantic representation in memory. A number of studies have demonstrated that the semantically based repetition priming approach cannot explain spacing effects in recognition memory for stimuli such as unfamiliar faces, and nonwords that are not amenable to semantic analysis (Russo, Parkin, Taylor, & Wilks, 1998; Russo et al, 2002; Mammarella, Russo, & Avons, 2005). Cornoldi and Longoni (1977) have even found a significant spacing effect in a forced-choice recognition memory task when nonsense shapes were used as target stimuli. Russo et al. (1998) proposed that with cued memory of unfamiliar stimuli, a short-term perceptually-based repetition priming mechanism supports the spacing effect. When unfamiliar stimuli are used as targets in a cued-memory task, memory relies on the retrieval of structural-perceptual information about the targets. When the items are presented in a massed fashion, the first occurrence primes its second occurrence, leading to reduced perceptual processing of the second presentation. Short-term repetition-priming effects for nonwords are reduced when the lag between prime and target trials is reduced from zero to six (McKone, 1995), thus it follows that more extensive perceptual processing is given to the second occurrence of spaced items relative to that given to massed items. Hence, nonsense items with massed presentation receive less extensive perceptual processing than spaced items; thus, the retrieval of those items is impaired in cued-memory tasks. Congruent with this view, Russo et al. (2002) demonstrated that changing the font in which repeated presentations of nonwords were presented reduced the short-term perceptual priming of those stimuli, especially for massed items. Upon a recognition memory test, there was no spacing effect found for the nonwords presented in different fonts during study. These results support the hypothesis that short-term perceptual priming is the mechanism that supports the spacing effects in cued-memory tasks when unfamiliar stimuli are used as targets. Furthermore, when the font was changed between repeated presentations of words in the study phase, there was no reduction of the spacing effect. This resistance to the font manipulation is expected with this two-factor account, as semantic processing of words at study determines performance on a later memory test, and the font manipulation is irrelevant to this form of processing. Mammarella, Russo, & Avons (2002) also demonstrated that changing the orientation of faces between repeated presentations served to eliminate the spacing effect. Unfamiliar faces do not have stored representations in memory, thus the spacing effect for these stimuli would be a result of perceptual priming. Changing orientation served to alter the physical appearance of the stimuli, thus reducing the perceptual priming at the second occurrence of the face when presented in a massed fashion. This led to equal memory for faces presented in massed and spaced fashions, hence eliminating the spacing effect. See also *memory bias *Zeigarnik effect *list of cognitive biases References * Whitten, W. B. & Bjork, R. A. (1977). Learning from tests: Effects of spacing. Journal of Verbal Learning & Verbal Behavior, 16, 465-478. * Appleton-Knapp, S. L., Bjork, R. A., & Wickens, T. D. (2005). Examining the spacing effect in advertising: Encoding variability, retrieval processes, and their interaction. Journal of Consumer Research, 32(2), 266-276. * Bird, C. P. (1987). Influence of the spacing of trait information on impressions of likability. Journal of experimental social psychology, 23(6), 481-497. * Cermak, L. S., Verfaellie, M., Lanzoni, S., Mather, M., & Chase, K. A. (1996). 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